1. Field of the Invention
The present invention relates generally to a method and apparatus for converting the potential energy stored in an upper reservoir of water into electrical energy during periods of high energy demand, use being made of a subterranean salt dome reservoir.
2. Brief Description of the Prior Art
Underground pumped storage facilities have been proposed wherein water from an upper reservoir flows through a subterranean shaft, through a subterranean hydroelectric power generator, and into an underground reservoir to produce electricity during periods of high energy demand. The water is then pumped back to the surface during periods of low energy demand by electric pumps which run on excess energy which would otherwise be wasted. Underground pumped storage facilities, however, have not been constructed because of the great cost required to excavate large underground reservoirs at depths which would be necessary for efficient underground pumped storage power generation.
Underground cavities excavated by solutionization have been used in the recovery of geotherman energy from below the earth, as evidenced, for example, by the patents to Jacoby U.S. Pat. No. 3,661,424 and 3,676,078. Water is introduced into the salt dome and dissolves the surrounding salt to form a reservoir in the dome. The water is then pumped out of the reservoir to form a hollow underground cavity. Heated air is extracted from the cavity and is passed through a heat-exchanger located on the surface so that the geothermal energy stored below the earth's surface may be utilized.